Many medical device applications require advancement of device in a reduced profile to a remote site within the body, where on reaching a target site the device assumes or is deployed into a relatively larger profile. Applications in the cerebral vasculature are one such example of medical procedures where a catheter advances from a remote part of the body (typically a leg) through the vasculature and into the cerebral region of the vasculature to deploy a device. Accordingly, the deployed devices must be capable of achieving a larger profile while being able to fit within a small catheter or microcatheter. In addition, the degree to which a physician is limited in accessing remote regions of the cerebral vasculature is directly related to the limited ability of the device to constrain into a reduced profile for delivery.
Treatment of ischemic stroke is one such area where a need remains to deliver a device in a reduced profile and deploy the device to ultimately remove a blockage in an artery leading to the brain. Left untreated, the blockage causes a lack of supply of oxygen and nutrients to the brain tissue. The brain relies on its arteries to supply oxygenated blood from the heart and lungs. The blood returning from the brain carries carbon dioxide and cellular waste. Blockages that interfere with this supply eventually cause the brain tissue to stop functioning. If the disruption in supply occurs for a sufficient amount of time, the continued lack of nutrients and oxygen causes irreversible cell death (infarction). Accordingly, immediate medical treatment of an ischemic stroke is critical for the recovery of a patient.
Naturally, areas outside of ischemic stroke applications can also benefit from improved devices. Such improved devices can assume a profile for ultimate delivery to remote regions of the body and can remove obstructions. There also remains a need for devices and systems that can safely remove the obstruction from the body once they are secured within the device at the target site. Furthermore, there remains a need for such devices that are able to safely removed once deployed distally to the obstructions in the even that the obstructions is unable to be retrieved.
Many physicians currently use stents to perform thrombectomy (i.e. clot removal). Typically, the physician deploys the stent in the clot, to attempt and push the clot to the side of the vessel and re-establish blood to flow. Tpa is often administered to dissolve the clot and is given in addition with the stem. Yet, if clot dissolution is ineffective or incomplete, the physician may attempt to remove the stent while it is expanded against the clot. In doing so, the physician drags the clot from the vessel and in a proximal direction into a guide catheter located in the patients neck (carotid artery). While this has shown to be effective in the clinic and easy for the physician to perform, there remain some distinct disadvantages using this approach:
First, the stent may not sufficient hold on the clot. In such a case, the clot might not move from the vessel. Second, the clot might mobilize from the original blockage site, but might not adhere to the stem during translation toward the guide catheter. This is a particular risk when translating through bifurcations, and the flow can migrate the clot (or pieces of the clot) into the branching vessel. Third, if the clot is successfully brought to the guide catheter in the carotid artery, the clot may be “stripped” from the stem as the stent enters the guide catheter. Fourth, dragging an open stent can be traumatic to the vessel. The stent is usually oversized compared to the vessel, and dragging this relatively fixed metallic structure can pull the arteries and/or strip the cellular lining from the vessel, causing damage. Also, the stent can become lodged on plaque on the vessel walls resulting in further vascular damage.
Accordingly, a need remains a need for improved devices to remove occlusions from body lumens and/or vessels.